In recent years, the speed of the operation of semiconductor chips is becoming increasingly higher due to advancement in the integrated circuit technology. In conjunction with this trend, there are cases where noise is superimposed on the power source wiring and the like, possibly resulting in erroneous operation. Accordingly, a capacitor is mounted on an upper surface or a lower surface of a wiring board on which the semiconductor chip is mounted, so as to eliminate the noise.
With the above-described technique, however, since it is necessary to mount the capacitor separately after the completion of the wiring board, the number of processes disadvantageously increases. In addition, there is a need to secure in advance a region where the capacitor is mounted on the wiring board, so that the freedom of the layout of other electronic components declines. Furthermore, because the region where the capacitor is mounted on the wiring board is restricted by other wiring and the like, the wiring distance between the capacitor and the semiconductor chip becomes long, so that the wiring resistance and inductance in the wiring become disadvantageously large.
For these reasons, a technique for incorporating the capacitor in the wiring board has been proposed. As technique for incorporating the capacitor in the wiring board, for example, there is a technique is which an opening is provided in a core board which constitutes a core of the wiring board, and the capacitor is accommodated in this opening.
In this technique, since it is necessary to fix the capacitor to the core board, a resin filler is filled in the gaps between the core board and the capacitor in a state in which the capacitor is disposed in the opening of the core board. Specifically, an adhesive tape is adhered to the reverse surface of the core board, and the capacitor is disposed in the opening of the core board so that the reverse surface of the capacitor will be adhered to the adhesive tape. The resin filler is filled in a state in which the position of the capacitor with respect to the core board is fixed by the adhesive tape.
However, since the thickness of end portions of a conventional capacitor is thinner than the thickness of the remaining portions, steps are formed at the end portions of the capacitor. For this reason, if the resin filler is filled, the resin filler unfavorably enters the reverse surface side of the capacitor. As a result, the resin filler comes into contact with outer terminals disposed on the reverse surface of the capacitor, so that there is a possibility of resulting in faulty conduction, or a step of removing that resin filler is disadvantageously required.
It should be noted that a capacitor has been disclosed in which an outer peripheral surface of an inner electrode layer is exposed from between ceramic layers (e.g., JP-A-2004-228190). However, since only the outer peripheral surface of one side of the inner electrode layer is exposed, it is considered that the aforementioned steps are not alleviated sufficiently. In addition, although a disclosure is given in JP-A-2002-280250 as to the suppression of stepped portions in a general capacitor, this is a type in which the inner electrode is exposed on the outer peripheral surface.